Liquid crystal displays and more recently thin film transistor displays are well known and used in many applications. These types of displays are commonly used in connection with computers, programmable controllers, calculators and other digital processors for displaying information.
For these types of displays to be effective, light must be transmitted through the back of the display panel toward the observer, who is in front of the display. This is known as backlighting and is also well known. Different types of light sources have been used for backlighting thin film transistor and liquid crystal displays, including light emitting panels of the type which is made of optical fibers usually woven into a mat and provided with a reflector layer at the rear surface of the mat so that the light from the panel is emitted out the front of the mat and through the display. A diffuser panel may be provided over the front of the mat to enhance dispersion and uniformity of the light emitted. In such panels, several layers of optical fiber mat may be provided, depending upon the intensity of the emitted light desired.
When a light emitting panel of this type is used for display backlighting, provision must be made for illuminating the light emitting panel itself. This is usually accomplished with halogen light bulbs or light emitting diodes. Halogen bulbs have the advantage of being able to provide high intensity light, but have the disadvantage of having a limited life which requires periodic replacement of the bulb. Because these bulbs have been provided inside the cabinet of a digital processor, access for replacing the bulbs has been difficult. Also, turning off the power to replace the bulbs has also had the disadvantage of causing down time of the digital processor.